This invention relates to a novel positive-working radiation sensitive resin composition and, more particularly, to a positive-working radiation sensitive resin composition containing a radiation sensitive novolak resin, suited for manufacture of a semiconductor integrated circuit, production of a display surface of a liquid crystal display device in a LCD panel, manufacture of a circuit substrate for a thermal head etc., and like use.
In the wide field of manufacturing a semiconductor integrated circuit such as a LSI, preparing a display surface of a liquid crystal display device in a LCD panel, manufacturing a circuit substrate for a thermal head etc., and like use, photolithography has so far been employed for forming microelements or conducting fine processing. In the photolithography, a positive- or negative-working radiation sensitive resin composition is used for forming a resist pattern. Of these radiation sensitive resin compositions, those compositions containing an alkali-soluble resin and a photosensitizer of quinonediazide compound are most popularly used as the positive-working radiation sensitive resin compositions. As such compositions, there are described compositions having different formulations as, for example, xe2x80x98novolak resin/quinonediazide compoundxe2x80x99 in many documents such as Japanese Examined Patent Publication Nos. S54-23570 (U.S. Pat. No. 3,666,473) and S56-30850 (U.S. Pat. No. 4,115,128), Japanese Unexamined Patent Publication Nos. S55-73045, S61-205933 and S62-51459, etc.
These compositions containing a novolak resin and a quinonediazide compound have so far been studied from the viewpoint of both novolak resins and photosensitizers. From the viewpoint of a novolak resin, there have been developed novel resins. In addition, radiation sensitive resin compositions having excellent properties have also been obtained by improving properties of conventionally known resins. For example, there are disclosed techniques providing a radiation sensitive resin composition having excellent properties by using a novolak resin with a particular molecular weight distribution in Japanese Unexamined Patent Publication Nos. S60-140235 and H1-105243 and by using a novolak resin from which low-molecular-weight components of the resin has been removed by fractionation in Japanese Unexamined Patent Publication Nos. S60-97347 and S60-189739 and Japanese Patent Publication No.2590342. From the viewpoint of a photosensitizer, various attempts have been made to develop novel quinonediazide compounds and novel quinonediazide sulfonates. Further, there have been proposed the improvement of the characteristics by a combination of a specific novolak resin and a quinone diazide sulfonate (e.g. Japanese Unexamined Patent Publication H9-90622) or a combination of a specific dissolution promoter and a quinonediazide sulfonate of an alkali- soluble resin such as novolak resin (e.g. Japanese Unexamined Patent Publication No.H10-69077). Above-mentioned Japanese Unexamined Patent Publication Nos. H9-90622 and H10-69077 describe generally that quinonediazide sulfonates are formed by use of quinonediazide compounds having a sulfonic acid group at the 4- or 5-position, and further that such sulfonates of quinonediazide compounds having a sulfonic acid group at the 4- or 5-position are used in combination, but there is no specific disclosure therein on the combined use thereof such as an effect when used in combination thereof, a mixing ratio thereof, and Examples.
A number of positive-working radiation sensitive resin compositions containing quinonediazide compounds have been put into practice as a result of various technical developments having so far been made, and the aspect ratio of thickness of radiation sensitive resin coating to line width resolved has been improved to about 5:1 .
On the other hand, degree of integration of semiconductor integrated circuits have been increased year by year and, in the manufacture thereof, processing of patterns with a line width of less than sub-micron order has become required. In the uses requiring such super-fine processing, good pattern reproducibility is required as well as high resolution and, from the standpoint of production cost, it is also required to improve throughput (yield per unit time) upon production by meeting the high sensitization. However, conventionally known radiation sensitive resin compositions can not satisfy these requirements at the same time, thus being a problem.
Under the circumstances with problems described above, an object of the present invention is to provide a positive-working radiation sensitive resin composition which has high sensitivity and high resolution and can form a good pattern.
As a result of intensive investigation, the inventors have found that in a positive-working radiation sensitive resin composition comprising a radiation sensitive novolak resin consisting of esterified products between an alkali-soluble novolak resin and naphthoquinonediazide compounds, if said radiation sensitive novolak resin consists of two kinds of esterified products between an alkali-soluble novolak resin and naphthoquinonediazide compounds different in the substitution position of the sulfonic acid group and the mixing ratio of the substituent group is in a specific range, the resulting positive-working radiation sensitive resin composition has high sensitivity, high resolution and ability to form excellent patterns, which cannot be predicted from the prior art, thus having completed the present invention based on the finding.
That is, the present invention relates to a positive-working radiation sensitive resin composition comprising partially esterified products (radiation sensitive novolak resin) between an alkali-soluble novolak resin and o-naphthoquinonediazide compounds, wherein said partially esterified products comprise 1,2-naphthoquinonediazide-4-sulfonic acid ester and 1,2-naphthoquinonediazide-5-sulfonic acid ester, and the ratio by weight of 4-sulfonyl group and 5-sulfonyl group bound to said partially esterified products ranges from 5:95 to 20:80.
The present invention will now be described more specifically below.
An alkali-soluble novolak resin used as a starting material for preparing the radiation sensitive novolak resin of the present invention is a novolak-type phenol resin, and is manufactured by polycondensation between one of phenols or a mixture thereof and an aldehyde such as formalin. The polycondensation between a phenol and an aldehyde may be conducted by any conventionally known processes such as using oxalic acid as a catalyst.
The alkali-soluble novolak resin may be the one from which low-molecular components were removed by suitable fractionation treatment such as re-precipitation. The removal of low-molecular components is conducted usually before the reaction between the alkali-soluble novolak resin and the naphthoquinonediazide compounds. Alternatively, after the reaction of the alkali-soluble novolak resin and the naphthoquinonediazide compounds, the reaction products may be treated in the same manner as in the above-mentioned fractionation treatment of the novolak resin, so that low-molecular components are removed from the reaction products, and the radiation sensitive novolak resin thus obtained is similar to the one obtained from the novolak resin from which low-molecular components were previously removed. However, from the viewpoint of safety and because of the possible inactivation of the radiation sensitive functional groups by heating at the time of fractionation treatment, the fractionation treatment is conducted preferably before the reaction. If the novolak resin from which low-molecular components were removed by fractionation treatment is used, desired resolution may not be achieved, so a predetermined dissolution inhibitor is preferably blended with it.
In the present invention, there are preferably used an alkali-soluble novolak resin having a dissolution rate of 10 to 300 xc3x85/sec, for a 2.38 wt% aqueous solution of tetramethylammonium hydroxide measured according to the following xe2x80x9cmethod of measuring dissolution rate of novolak resinxe2x80x9d. If the dissolution rate of the alkali-soluble novolak resin is less than 10 xc3x85/sec, such novolak resin can cause reduction in sensitivity and remaining of indissoluble substances. In addition, it is difficult to attain high resolution by use of such novolak resin. If the dissolution rate is more than 300 xc3x85/sec, such novolak resin is not preferable for the resist pattern by reason of much decrease in resist film thickness after development, and it is difficult to obtain resist patterns with good reproducibility and a good profile of patterns by use of such novolak resin. (Method of measuring dissolution rate of novolak resin)
20 g of novolak resin is dissolved in 80 g of a mixed solvent of ethyl lactate/n-butyl acetate (85/15), then filtered through a 0.5 xcexcm Teflon filter. The resulting resin solution is applied on a HMDS-treated 4-inch silicon wafer using a spin coater, LARC ULTIMA-1000 made by Lithotec Japan Co. and baked at 100xc2x0 C. for 90 seconds on a hot plate to form a 1xcexcm-thick resist coating. Thickness of the coating is accurately measured by means of an apparatus for measuring film thickness, Lambda Ace made by Dainippon Screen Co., Ltd. Thereafter, the thus obtained silicon wafer is dipped in an alkaline developer solution, AZ(copyright) 300MIF Developer (a 2.38 wt % aqueous solution of tetramethylammonium hydroxide) made by Clariant (Japan) K.K. at 23 xc2x0 C., and the time necessary for the resin coating on the wafer to be completely dissolved is measured. Dissolution rate of novolak resin is calculated from the coating thickness and the dissolution time thus measured.
As the phenols to be used for manufacturing above-described alkali-soluble novolak resins, there maybe illustrated cresols such as o-cresol, p-cresol and m-cresol; xylenols such as 3,5-xylenol, 2,5-xylenol, 2,3-xylenol and 3,4-xylenol; trimethylphenols such as 2,3,4-trimethylphenol, 2,3,5-trimethylphenol, 2,4,5-trimethylphenol and 3,4,5-trimethylphenol; t-butylphenols such as 2-t-butylphenol, 3-t-butylphenol and 4-t-butylphenol; methoxyphenols such as 2-methoxyphenol, 3-methoxyphenol, 4-methoxyphenol, 2,3-dimethoxyphenol, 2,5-dimethoxyphenol and 3,5-dimethoxyphenol; ethylphenols such as 2-ethylphenol, 3-ethylphenol, 4-ethylphenol, 2,3-diethylphenol, 3,5-diethylphenol, 2,3,5-triethylphenol and 3,4,5-triethylphenol; chlorophenols such as o-chlorophenol, m-chlorophenol, p-chlorophenol and 2,3-dichlorophenol; resorcinols such as resorcinol, 2-methylresorcinol, 4-methylresorcinol and 5-methylresorcinol; catechols such as 5-methylcatechol; pyrogallols such as 5-methylpyrogallol; bisphenols such as bisphenol A, B, C, D, E or F; methylol-cresols such as 2,6-dimethylol-p-cresol; naphthols such as xcex1-naphthol, xcex2-naphthol, etc.; and the like. These are used independently or as a mixture of two or more thereof.
As the aldehydes, there may be used salicylaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde, hydroxybenzaldehyde, chloroacetaldehyde, etc. as well as formalin. These are used independently or as a mixture of two or more thereof.
On the other hand, 1,2-naphthoquinonediazide-4-sulfonic acid esters and 1,2-naphthoquinonediazide-5-sulfonic acid esters constituting the radiation sensitive novolak resin of the present invention can be produced in an arbitrary method known in the art. These are produced generally by dissolving, in a solvent, 1,2-naphthoquinonediazide-4-sulfonyl halide and/or 1,2-naphthoquinonediazide-5-sulfonyl halide along with the alkali-soluble novolak resin described above, followed by introducing a base such as triethylamine into the mixture. Because the reaction proceeds almost quantitatively, the amount of 1,2-naphthoquinonediazide-4-sulfonyl halide or 1,2-naphthoquinone diazide-5-sulfonyl halide used in the reaction system can be regulated to control the amount of the ester substituent groups.
Preferable examples of 1,2-naphthoquinonediazide-4-sulfonyl halides includes 1,2-naphthoquinonediazide-4-sulfonyl chloride and preferable examples of 1,2-naphthoquinonediazide-5-sulfonyl halides include 1,2-naphthoquinonediazide-5-sulfonyl chloride in the present invention.
As to reaction substitution ratio of the naphtoquinonediazide compound to the alkali-soluble novolak resin, 3.5 to 25 mol % based on hydrogen atom of hydroxyl group of said novolak resin is preferred, with 4 to 15 mol % being more preferred. If the reaction substitution ratio is less than 3.5 mol %, intended resolution is hardly attained, whereas if more than 25 mol %, there results a positive pattern with development residues and tends to form a worse pattern profile.
In the present invention, the 1,2-naphthoquinonediazide-4-sulfonyl group and 1,2-naphthoquinonediazide-5-sulfonyl group described above are preferably used as a mixture in a ratio by weight of from 5:95 to 20:80. If the ratio of the 1,2-naphthoquinone diazide-4-sulfonyl group is less than 5%, the resulting composition is poor in resolution, and during development, scum is generated and the microgrooving characteristics are deteriorated. On the other hand, if the ratio of the 1,2-naphthoquinonediazide-4-sulfonyl group exceeds 20%, the shape of patterns is deteriorated. The mixture of 1,2-naphthoquinonediazide-4-sulfonic acid ester and 1,2-naphthoquinonediazide-5-sulfonic acid ester can be produced by separately reacting each of their corresponding naphthoquinonediazide compounds with the novolak resin to produce 1,2-naphthoquinonediazide-4-sulfonic acid ester or 1,2-naphthoquinonediazide-5-sulfonic acid ester followed by mixing thereof, or by allowing the naphthoquinonediazide compounds previously mixed in a predetermined ratio to react with the novolak resin. However, it is preferable to use the former method wherein 1,2-naphthoquinonediazide-4-sulfonic acid ester and 1,2-naphthoquinonediazide-5-sulfonic acid ester are separately produced and then mixed.
The solvent for dissolving the radiation sensitive novolak resin of the present invention includes ethylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether; ethylene glycol monoalkyl ether acetates such as ethylene glycol monomethyl ether acetate and ethylene glycol monoethyl ether acetate; propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether and propylene glycol monoethyl ether; propylene glycol monoalkyl ether acetates such as propylene glycol monomethyl ether acetate and propylene glycol monoethyl ether acetate; lactates such as methyl lactate and ethyl lactate; aromatic hydrocarbons such as toluene andxylene; ketones such as methyl ethyl ketone, 2-heptanone and cyclohexanone; amides such as N,N-dimethylacetamide and N-methylpyrrolidone; and lactones such as xcex3-butyrolactone. These solvents can be used independently or as a mixture of two or more thereof.
A photosensitizer containing a quinonediazide group other than 1,2-naphthoquinonediazide-4-sulfonic acid ester and 1,2-naphthoquinonediazide-5-sulfonic acid ester described above may be incorporated into the positive-working radiation sensitive resin composition of the present invention as necessary. These photosensitizers are obtained by allowing naphthoquinonediazidesulfonyl halide or benzoquinonediazidesulfonyl halide to react with a low-molecular or high-molecular compound having a functional group capable of condensation reaction with these sulfonyl halides. The functional group that can be condensed with a sulfonyl halide includes a hydroxyl group, an amino group etc. Among these, a hydroxyl group is particularly preferable. The compounds containing a hydroxyl group include e.g. hydroquinone; resorcinol; hydroxybenzophenones such as 2,4-dihydroxybenzophenone, 2,3,4-trihydroxybenzophenone, 2,4,6-trihydroxybenzophenone, 2,4,4xe2x80x2-trihydroxybenzophenone, 2,3,4,4xe2x80x2-tetrahydroxybenzophenone, 2,2xe2x80x2,4,4xe2x80x2-tetrahydroxybenzophenone and 2,2xe2x80x2,3,4,6xe2x80x2-pentahydroxybenzophenone; hydroxyphenylalkanes such as bis(2,4-dihydroxyphenyl)methane, bis(2,3,4-trihydroxyphenyl)methane and bis(2,4-dihydroxyphenyl)propane; and hydroxytriphenylmethanes such as 4,4xe2x80x2,3xe2x80x3,4xe2x80x3-tetrahydroxy-3,5,3xe2x80x2,5xe2x80x2-tetramethylphenylmethane and 4,4xe2x80x2,2xe2x80x3,3xe2x80x3,4xe2x80x3-pentahydroxy-3,5,3xe2x80x2,5xe2x80x2-tetramethyltriphenylmethane. These can be used independently or as a combination of two or more thereof.
A low-molecular compound which has a phenolic hydroxyl group or groups may be incorporated as a dissolution inhibitor of a radiation sensitive resin composition in the positive-working radiation sensitive resin composition of the present invention. And there are illustrated, for example, 4,4xe2x80x2,4xe2x80x3-methylidinetrisphenol, 2,6-bis[(2-hydroxy-5-methylphenyl)methyl]-4-methylphenol, 4,4xe2x80x2-[1-[4-[1-(4-hydroxyphenyl)-1-methylethyl]phenyl]ethylidene]bisphenol, 4,4xe2x80x2,4xe2x80x3-ethylidinetrisphenol, 4-[bis(4-hydroxyphenyl)methyl]-2-ethoxyphenol, 4,4xe2x80x2-[(2-hydroxyphenyl)methylene]bis[2,3-dimethylphenol], 4,4xe2x80x2-[(3-hydroxyphenyl)methylene]bis[2,6-dimethylphenol], 4,4xe2x80x2-[(4-hydroxyphenyl)methylene]bis[2,6-dimethylphenol], 2,2xe2x80x2-[(2-hydroxyphenyl)methylene]bis[3,5-dimethylphenol], 2,2xe2x80x2-[(4-hydroxyphenyl)methylene]bis[3,5-dimethylphenol], 4,4xe2x80x2-[(3,4-dihydroxyphenyl)methylene]bis[2,3,6-trimethylphenol], 4-[bis(3-cyclohexyl-4-hydroxy-6-methylphenyl)methyl]-1,2-benzenediol, 4,6-bis[(3,5-dimethyl-4-hydroxyphenyl)methyl]-1,2,3-benzenetriol, 4,4xe2x80x2-[(2-hydroxyphenyl)methylene]bis[3-methylphenol], 4,4xe2x80x2,4xe2x80x3-(3-methyl-1-propanyl-3-ylidine)trisphenol, 4,4xe2x80x2,4xe2x80x3,4xe2x80x2xe2x80x3-(1,4-phenylenedimethylidine)tetrakisphenol, 2,4,6-tris[(3,5-dimethyl-4-hydroxyphenyl)methyl]-1,3-benzenediol, 2,4,6-tris[(3,5-dimethyl-2-hydroxyphenyl)methyl]-1,3-benzenediol, 4,4xe2x80x2-[1-[4-[1-[4-hydroxy-3,5-bis[(hydroxy-3-methylphenyl)methyl ]phenyl]-1-methylethyl]phenyl]ethylidene]bis[2,6-bis(hydroxy-3-methylphenyl)methyl]phenol, and the like. If these low-molecular compounds having phenolic hydroxyl group or groups are used, they are used in an amount of usually 2 to 20 parts by weight relative to 100 parts by weight of the radiation sensitive novolak resin.
Dyestuffs, adhesive aids, surfactants etc. conventionally used as additives of the positive-working radiation sensitive resin composition may be incorporated as necessary into the positive-working radiation sensitive resin composition of the present invention. The dyestuffs include e.g. Methyl Violet, Crystal Violet, Malachite Green etc.; the adhesive aids include e.g. alkyl imidazoline, butyric acid, alkyl acid, polyhydroxystyrene, polyvinylmethyl ether, t-butyl novolak, epoxy silane, epoxy polymer, silane etc.; and the surfactants include e.g. nonionic surfactants such as polyglycols and derivatives thereof such as polypropylene glycol, polyoxyethylene lauryl ether etc., fluorine-containing surfactants such as Fluorad (trade name; manufactured by Sumitomo 3M Ltd.), Megafac (trade name; manufactured by Dainippon Ink and Chemicals, Inc.), Sulflon (trade name; manufactured by Asahi Glass Co., Ltd.) or organosiloxane surfactants such as KP341 (trade name; Shin-Etsu Chemical Co., Ltd.).
Furthermore, the positive-working radiation sensitive resin composition of the present invention may be used in combination with an inorganic anti-reflective coating of TiN, SiN, SiON or the like or an organic anti-reflective coating of AZ(copyright) BARLi, AZ(copyright) BARLi II (manufactured by Clariant (Japan) K.K.).
The positive-working radiation sensitive resin composition of the present invention is applied on a substrate such as a silicon wafer having an anti-reflective coating thereon, by spin coating or the like, and the substrate on which the radiation sensitive resin composition has been coated is subjected to baking to form a radiation sensitive resin coating. The substrate having thereon the radiation sensitive resin coating is exposed with radiation such as ultraviolet rays, deep ultraviolet rays, X-rays or electron beams and is developed with an alkaline developing solution to form a resist pattern with high resolution and good pattern profile.